Cigarette paper



L A n N O R R A H D w CIGARETTE PAPER Filed Sept. 16, 1944 3 venters:

this Gttorneg,

Patented Apr. l1, 1950 UNITED STATES PATENT OFFICE CIGARETTE PAPER Application September 16, 1944, Serial N0. 554,510

. 2 Claims. (Cl. 92-3) Cigarette paper manufactured for use in machine made cigarettes is commonly of the combustible type, that is, it will burn easily when rolled in the regular cigarette in contact with cigarette tobacco. This type of cigarette does not require a forced draft or continued pulling by the smoker, but once lighted it will continue to burn until the entire cigarette is consumed.

The means employed to establish this continuous burning property ci the cigarette paper in the rolled cigarette. is an alkaline ller, commonly referred to as chalk, which is incorporated in the cigarette paper sheet during manufacture thereof. A typical example of an alkaline ller is calcium carbonate that is added to the paper pulp suspension while the latter is in the beater or in the machine chest or just prior to formation of the pulp into a continuous paper web or sheet on the paper machine. The amount of filler used will vary with dierent grades and types of cigarette paper, and may commonly constitute about to 30% of the total weight of the iilled cigarette paper of the combustible type.

This cigarette paper containing the carbonate or other suitable types of filler is referred to in the trade as a iilled" paper. The ller has other advantages in addition to rendering the paper easily burnable. For example, it makes the paper more opaque and thereby produces a better appearing cigarette; also, it increases the drying rate of the cigarette paper on the paper machine so that greater production can thereby be obtained.

Along with these advantages, however, the filled cigarette paper has the disadvantage of being relatively weak when wet. The lled paper sheet is highly absorbent of moisture and after absorbing a substantial amount of water, which it will do very rapidly, it becomes relatively weak. In actual use this property shows up when the cigarette is smoked since the saliva in the smokers mouth quickly wets the paper. Now, if the paper is too low in strength when it is wetted in the smokers mouth the wet portion will pull away from the remaining dry portion of the paper and oftentimes stick to the smokers lips. With certain types of smokers who chew or wet the end of the cigarette excessively, the cigarette paper of low wet strength will disintegrate too easily in the smokers mouth.

In view of these characteristics of high quality cigarette paper when wet, it has been an important commercial problem to maintain all of the desirable properties of the cigarette paper etc., and at the same time impart to the paper sufllcient resistance to weakening or disintegration when it becomes wet in the smokers mouth. Certain chemicals which would be helpful in establishing higher wet strength properties, cannot be used in the normal manner because of the alkaline character of the cigarette paper, which is imparted to the paper by the substantial amount of alkaline-filler in the paper web. For example, it is not practical to incorporate acid catalyzed resins in the cigarette paper pulp while in the beater or machine chest, as is commonly done for other types of paper, since the acid or acid salt thus used would attack the carbonate filler.

In accordance with the present invention we have discovered a method and means for increasing the resistance of cigarette paper to disintegration when it becomes wet in the smokers mouth. For this purpose the normal wet strength of the paper needs to be increased by a controlled amount since excessive strengthening would harm other desirable or necessary properties of the paper.

While this improvement in cigarette paper in accordance with our invention may be referred to as an increase in wet strength, it should not be confused with the usual wet strength processes wherein resins, cellulose ethers, etc., are used for imparting to the paper a wet strength as great as 50% to 100% of the dry strength of the paper. Such wet strength values are commonly used in map paper, blueprint paper, moist food wrappers, tea bag paper. paper towels, etc. In contrast thereto the wet tensile strength of the improved paper of our invention may be in the order of 5% of the dry tensile strength of the paper. Nevertheless, this renders the paper sufficiently resistant to the common deleterious effects of moisture during smoking, and at the same time does not adversely affect the necessary porosity, opacity and many other required physical characteristics of high grade cigarette paper.

We have found that we can obtain this desired, relatively slight, increase in wet tensile strength of the cigarette paper, as compared with the dry tensile strength, by application of a very dilute aqueous solution of an urea formaldehyde polymer and an acid salt to the paper web. This solution is applied advantageously by means of a size press, to the partially dry paper web during the drying of the paper on a Fourdrinier paper machine. However, the application of the solution may be eiected in other suitable ways, such such as easy burning, thinness. purity, whiteness, as by spraying, transfer rolls, etc. Also it may take place at any location in the dryer section oi the paper machine or just prior thereto.

The amount of urea formaldehyde resin polymer which we use is almost inilnitesimally small has the desired wet strength value practically by the time it comes of! of the paper machine. Some slight increase in wet strength may take place during subsequent storage of the paper.

as compared with the usual amounts of 1% to 5 In actual commercial use of our invention we or more of this resin for producing high wet have obtained very good results when using acid strength map paper or wrapping paper. As conammonium salts for acidifying the resin solution. trasted with this, we use resin amounts of less Specific examples of such salts are monoamthan one-tenth of 1% of the weight of the paper; monium phosphate, diammonium phosphate and a typical amount being represented by 0.025% of 1o ammonium sulfate. These salts may be used resin based on the weight of the finished dry singly or in different combinations and satisfacpamn tory results obtained. Our experience shows that As far as we are advised it has heretofore been at least one acid salt is necessary since heat alone considered impossible or impractical to use resins is not sufficient to set the resin and obtain the for producing high wet strength values in paper desired increase in wet strength, during manuhaving such high alkaline ller content that the facture of the paper on the paper machine. The urea formaldehyde resin could not be catalyzed following table shows pertinent data and illusunder the usual acid conditions. In the usual trates the effects of the different acid salts in practice the setting of such resins is catalyzed by combination with the urea formaldehyde resin, the presence of suilicient acid or acid salt to in varying amounts. Table P c t' P mp {gg} er en m Bp" sglgn Pggf meriti R' MAP* DA1 As' Strength 1 o 0 0 9.3 105 A 2 .025 0 0 0 7.a 0.3 i a .25 .oe .31 0.0 8.5 115 4 025 .o1 0 0 0.1 9.a 110 5 .025 .0a 0 0 5.7 0.3 120 B 0 .025 .00 0 0 5.4 0.1 135 7 .025 .22 0 0 5.0 8.9 140 s .025 .a1 0 0 4.0 2.1 10o o .025 .sa 0 0 4.7 a2 15o C 10 .025 0 .a1 0 1.a 8.a 150 11 .025 0 .030 o 7.1 8.0 150 D 12 .025 0 0 .a1 4.o 8.0 140 1a .025 o 0 .e30 4.1 as 150 14 .012 .25 .00 .s1 0.0 8.5 135 10 .02s .25 .oe .31 0.0 8.5 150 1: 10 .050 .25 .00 .31 0.0 a5 20o 17 .100 .25 .00 .31 0.1 8.5 200+ is .200 .25 .o0 .31 0.0 8.5 200+ R=Urea formaldehyde resin. MAP-Monoammonium phosphate. DAPI-Diammonium phosphate. ASH-Ammonium Sulfate.

produce an acid pH in the pulp suspension or paper sheet.

The carbonate illled cigarette paper to which the treatment of our invention is applied to render it resistant to disintegration in the smokers mouth, is normally definitely alkaline. For example, the untreated paper with carbonate filler will have a pH value of about 9.3. After treatment in accordance with our invention the iinished paper has a somewhat lower pH value, such as for example 8.5, but is still deilnitely alkaline As indicated in the above table, the test results 45 have been grouped into ve groups A, B, C. D and E. The group A is a miscellaneous group and shows that without any treatment of the paper the wet strength value is relatively low; that use of the resin alone, without any acid salt, will not give the desired increase in wet strength; and that use of the acid salts alone, without any resin. will likewise not give the desired increase in wet strength.

Group B shows the results obtained when using because of the large, alkaline illler content. a single acid salt, i. e., monoammonium phos- Despite this alkaline characteristic of y the phate, in varying amounts, and in combination paper we have been able to set the urea i'ormaldewith a constant amount of the urea formaldehyde resin polymer in the paper during the rapid hyde resin. It will be noted that the wet tensile manufacture thereof on the paper machine, and strength of the paper so treated increases with obtain the desired amount of increase in wet so the increasing amounts of the monoammonium strength of the cigarette paper. An illustrative phosphate, and the solution pH and paper pH but non-limiting example of this increase is a decrease with thel increasing amounts of the wet strength value of for the untreated paper monoammonium phosphate. The higher and and for the treated paper, as determined by more desirable wet strength values, e. g. 150, are an accurate wet strength test. es obtained with the higher percentages of 'the We have been able to obtain these satisfactory monoammonium phosphate and lower pH values results in the alkaline cigarette paper, by acidifyof the resinous solution. ing the aqueous resin polymer solution with a In group C another acid salt is used, namely, suitable amount of a Water soluble acid salt; diammonium phosphate. The results here show applying this acidiiled, aqueous resin solution to 7o that desirable wet' strength can be obtained with the paper web, and then heating it promptly to as little as 0.31% of diammonium phosphate and dry the paper and set the resin. The combination 0.025% of resin in the paper. of the acid salt and heat (of drying on the paper Group D is the same as group C except that machine) effects quick setting of the resinv so ammonium sulfate is used as the acidammonium that the paper which is impregnated therewith 7s salt and gives substantially the same results as the diammonium phosphate shown in group C. The ammonium sulfate being a salt of a stronger acid gives a lower solution pH value than is obtained with the diammonium phosphate salt. It is interesting to note in this regard that the desired wet strength values are obtainable with solutions having acid pH values of as low as about 4 and as high as about 7.8.

The test data in group E show the results obtained when using all three of the acid salts, namely, monoammonium phosphate, diammonium phosphate and ammonium sulfate, in combination with varying amounts of the urea formaldehyde resin. In certain respects, this combination is the most advantageous since it provides desirable high wet strength values, gives a relatively high acid pH value in the treating solution, and lowers the pH value of the ilnal paper to about 8.5. These data also show that if a wet strength value of about 150 is desired, it is not necessary to increase theamount of resin above the inflnitesimally small amount of 0.025% since such an amount will give a wet strength value of about 150. Larger amounts of resin give higher wet strength values that are not needed for the purpose of preventing disintegration of the cigarette paper when it becomes wet in the smokers mouth, as discussed above.

A supplemental advantage of the use of all three of the ammonium salts shown in group E is the improvement produced thereby in the burnlng and ash characteristics of the cigarette paper. These latter features are disclosed in our copending application Serial No. 511,692, nled November 25, 1943, now abandoned. It is of advantage that this combination of the three salts with the urea formaldehyde resin may be used for acidifying the resin and increasing the wet strength in accordance with our present invention, and concomitantly produce the improvement in features disclosed in our said copending application. However, it is to be understood from the above data that the present invention is not dependent upon the use of all three of these salts or, in fact, upon the combination of two or more of these salts. As above shown, any one of the salts taken alone will serve satisfactorily to set the resin and thereby make possible the increase in wet strength of the paper which characterizes our present invention.

A typical but non-limiting example of the procedure followed in treating cigarette paper in accordance with our invention is as follows. An ammonium salt, for example monoammonium phosphate, in amount of 3.14 lbs. is dissolved in a suitable small amount of water and the resulting solution is diluted to 50' gallons in a suitable tank. Into this solution is added 1;/8 of a pound, on a dry weight basis, of urea formaldehyde resin polymer. The polymer is in the form of a clear, syrupy liquid. It will be noted that the amount of ammonium salt here used is large with respect to the amount of ureaformaldehyde. Both the ammonium phosphate and the urea formaldehyde polymer are easily dissolved in the water solution. The resulting 50 gallons of aqueous resin and salt solution is applied by size press operation at a controlled rate such that it will treat 500 pounds of finished dry paper. This is accomplished by use of the equipment illustrated in the accompanying drawing and in accordance with the following description.

As shown in the single diagrammatic view, the composition is applied at an intermediate position in the drying end of a Fourdrinier paper machine. In other words, the applicator or sin press, indicated generally at Il, is located after the rst few drying rolls and before the several remaining drying rolls. We have obtained good results with a size press located between the fifth drying roll, such as indicated at I I, and the sixth drying roll, such as indicated at I2, of a machine having ten drying rolls.

The specic location of the size press is important mainly from the standpoint of applying the composition to the paper when the latter has the proper or most desirable moisture content as referred to hereinabove. In one specic, but non-limiting commercial application, we have obtained very desirable results with paper having a moisture content of about 50%. as it leaves the drying roll Il, and a moisture content of about 65% after application of the chemical composition at the size press l0 or just before the treated paper reaches the next drying roll I2.

The applicator system comprises a box member i3 containing the chemical composition I4, which is continually supplied through a suitable conduit indicated at l5 and connected with a pump i6 and supply tank l1. The pump i6 maintains continuously the desired level of liquid composition in the box or trough i3. The continuous overiiow of liquid is returned through a conduit i8 which projects upward into the trough I3 to the desired overow level. A metal pick-up roll is rotates in contact with the composition il and in fact takes the place of one' side member of the trough i3. The thin liquid composition picked up by the roll i8 is brought into contact with the moist web of paper 20 and causes good permeation and impregnation of the paper sheet. Furthermore, the paper sheet or web, as it reaches the size press, still contains considerable water and the wet web is very receptive to further wetting with the composition.

To effect impregnation and to remove the excess liquid from the paper web, a rubber covered press roll 2| is superimposed on the roll I9. The principal amount of the excess liquid ows back over the upper left portion of the roll I9 and into the supply trough I3. Some lesser amount of the excess liquid drips from the roll I and is caught by the strainer member 22 and is returned to the supply through conduit 2l. After the treated paper passes around the drying roll l2 and similar succeeding drying rolls it is ready to be wound up and used.

Various m'odications and changes may be made in the above described materials, products and procedures without departing from the scope of our invention as dened in the appended claims.

We claim:

l. A combustible, non-waterproofed, highly water absorbent cigarette paper having a pH of about 8.5, containing about 20-30% of calcium carbonate based on the weight of the filled cigarette paper, and polymerized urea formaldehyde resin in an amount from between about 0.025% to about 0.10% which effects an increase of about 50% to 100% in the wet strength of the cigarette paper.

2. A combustible, non-waterproofed, easily water-absorbent cigarette paper having suilicient wet strength to prevent disintegration when wet in the smokers mouth, said paper having a pH of about 8.5 to 9.3 and containing about 20% to 30% calcium carbonate illler, about 0.025% to 0.10% urea formaldehyde resin polymer based on the weight of the filled cigarette paper, about .0.01% to 0.88% of n. wuter soluble ocld um- Number Nume Duse monium salt that eects setting of nld urea 2.815.128 Newkirk 1hr. 30, 1942 formaldehyde resin polymer, und sold :mount o! 2,322,887 Bchwu'tx June 29, 1242 polymer en'ects an increase of about 50% to 200% 2,335,302 Britt July 27, 1942 in the wet strength ot the ollnrette pper. 5 2.338.602 Schur Jun. 4. 1944 WARD D. HARRISO nonmsoN n. MATTHEWS. FOREIGN PATENTS Number Country Date REFERENCES CITED 402,346 Great Britain Nov. 30, 1933 The following references are of record in the 0 502,855 an Brink* ml- 311 1939 me of aus patent: 523,185 Great Bumm July s, mo

UNITED srA'rEs PATENTS OTHER REFERENCES vNumber Name Date Paper Trade Journal, vol. 11'1, No. 23, pp. 27-32, 11:70.25@- McKee Au.s,19a2 ,5 Dec.2.1943. 1,953,832 Sanden Apr. 3, 1934 The Ufoxmites for Paper, published by The 2,002,317 Strain Sept. 14, 1937 Resnous Products I: Chemical Company, Phila- 2,300,089 Bauer et al. Jan. 26, 1943 delphia., Pl.. 

1. A COMBUSTIBLE, NON-WATERPROOFED, HIGHLY WATER ABSORBENT CIGARETTE PAPER HAVING A PH OF ABOUT 8.5, CONTAINING ABOUT 20-30% OF CALCIUM CARBONATE BASED ON THE WEIGHT OF THE FILLED CIGARETTE PAPER, AND POLYMERIZED UREA FORMALDEHYDE RESIN IN AN AMOUNT FROM BETWEEN ABOUT 0.025% TO ABOUT 0.10% WHICH EFFECTS AN INCREASE OF ABOUT 50% TO 100% IN THE WET STRENGTH OF THE CIGARETTE PAPER. 